Question 995874
x = number of mL of the first solution.
y = number of mL of the second solution.


.2x = number of mL of acid in the first solution.
.4y = number of mL of acid in the second solution.


the total mL in your final solution is x + y.


the total mL of acid in your final solution is .2x + .4y.


you know that x is equal to 75mL and you know that y is equal to 50mL.


you can replace x and y with those figures in your formulas as shown below:


x + y becomes 75 + 50 which becomes 125mL.


.2x + .4y becomes .2*75 + .4*50 which becomes 15 + 20 which becomes 35mL.


you have 35mL of acid in your final solution out of a total of 125mL in your final solution.


the percentage of acid is therefore equal to 35/125 = 7/25 = .28 * 100 = 28%.